Second-year quarterback Russell Wilson, leading the second youngest team ever to play in a Super Bowl, completed 18 of 25 passes for 206 yards, two touchdowns and no interceptions.

"We believed that we could get here," Wilson said.

"At the beginning of the season I told our guys, 'Hey, why not us?'

"We had the talent. We had the coaching. We have the best fans in the National Football League. We wanted to win it all."

His counterpart Manning was left red-faced after being caught unawares by the first offensive snap of the game which sailed over his head into the end zone for a safety to give the Seahawks a 2-0 lead.

The score came after just 12 seconds, the fastest in Super Bowl history.

Denver had to kick off, and Seattle was soon threatening again when wide receiver Percy Harvin gained 30 yards on a reverse play.

The Seahawks eventually settled for a 27-yard field goal to extend the lead to 5-0.

Seattle's defence maintained the momentum, forcing a three-and-out by Denver and then the offence drove for another for field goal to lead 8-0 at the end of the opening quarter.

While the focus before the game was on Seattle's running-back Marshawn Lynch, Wilson was giving the Denver secondary a hard time, making big plays to receivers Percy Harvin and Doug Baldwin.

Turnovers the key to Seattle triumph

It got worse for Denver, with Manning pressured into a poor pass that was picked off by Seattle safety Kam Chancellor.

Early in the second quarter the Seahawks made the Broncos pay, with Lynch going over for a 1-yard touchdown run to make it 15-0.

Denver finally got the chains moving on a drive downfield, but Manning was intercepted once again, with Malcolm Smith returning it 69 yards for a touchdown.

At 22-0 down, the game appeared all but over for Denver, and when Manning had one more shot before half-time, he and the Broncos were stopped on a 4th and 2 play to end a half from hell.

The second half started with Denver desperate to make inroads, but their determination lasted a few seconds, as Harvin took the opening kickoff back 87 yards for another Seattle score.

The rest was a formality.

Seattle forced another turnover, and Jermaine Kearse completed a great catch before spinning out of tackles to add a 23-yard touchdown.

Broncos avoid shutout, but no chance of comeback

The Broncos were reduced to trying to avoid a shutout, and they achieved this at the end of the third quarter, with a 14-yard pass from Manning to Demaryius Thomas.

A two-point conversion made it 36-8, but there was no fairytale comeback in the offing, as Wilson threw a 10-yard touchdown pass to Baldwin to restore the margin.

Manning ended the game with a Super Bowl-record 34 completed passes, but it was a meaningless stat. Seattle forced a fumble from Manning late in the game, with the defence allowing just eight points for the day.

"We knew they were fast. It was still a matter of us doing our jobs better and we didn't do that tonight," said Manning, who failed in his attempt to win a second Super Bowl ring and who fell to 11-12 in his career postseason record.

"I think we played a great football team. We needed to play really well in order to win and we didn't come anywhere close to that."

"Man, it's incredible, it's just a tremendous feeling," said Smith, who also secured Seattle's NFC title clinching victory over San Francisco by intercepting a last-gasp pass that was tipped by team-mate Richard Sherman.

"It's the way our defence is set up. We just run to the ball. I'm just the one today.

"It happens all the time like this. It feels great."

The Seahawks had lost their only previous appearance in the Super Bowl, going down to the Pittsburgh Steelers in Super Bowl XL.

Australian defensive lineman Jesse "Tha Monsta" Williams was selected by the Seahawks in last year's NFL draft after winning two national college championships with Alabama.

Williams was placed on the injured reserves list by the Seahawks in August 2013 with a knee injury, but is in line to receive a Super Bowl ring.

The result was Denver's fifth Super Bowl loss, going alongside the Broncos' two title wins in Super Bowls XXXII and XXXIII.

It was Denver's worst performance in a Super Bowl since being beaten 55-10 by the San Francisco 49ers in Super Bowl XXIV in January 1990.